Time for an update. I haven’t had so much time birding during the last few days. But I managed to check some harbours today. In Kollafirði there were about 200 Black-headed Gulls but not one single Iceland Gull.
In Hvalvík there were 15 Iceland Gulls and in Klaksvík there were about 30 Iceland Gulls present. So it really seems like the invasion is fading out at last. We’ve had strong winds from the south for almost a week, so my guess is that many of the birds have moved further north again.
It is hard to predict the furture, but my guess is that unless we get some serious westerly winds the invasion has now peaked and numbers are declining. This being said there are still a lot of birds south of us, so maybe these birds will pass by the Faroes in the months to come.
There still is a lot of discussion about how to identify Kumlien’s Gulls. Some are open to call all birds with dark markings on the primaries Kumlien’s Gulls while others think, that Iceland Gulls can show dark markings on the primaries. In order to get an identifiable Kumlien’s Gull you need an adult with some dark on the outer primaries or a subadult with a dark pattern somehow resembling that of Thayer’s Gull.
I do believe that all the non-adult Iceland Gull plumages can contain some kind of markings on the outer primaries. The 2w Glaucous Gull above undergoes that same moult as Iceland Gulls. I’ve seen several of these Glaucous Gulls with dark outer webs on the primaries and even a tendency to dark primary tips too. There is no such thing as a Glaucous Gull ssp. kumlieni, so I think it is safe to say, that birds that have pure white primaries as adults in deed can have some markings on the primaries earlier in life which is age related.
In short: If Glaucous Gulls can show these markings then it does not make sence the Iceland Gulls cannot show it without being ssp. kumlieni.
So what does it take to make a safe id of a 2w Kumlien’s Gull? Look at the picture above. There is a very clear contrast between inner and outer primaries and the mirror on p10 is already visible. Furthermore p5-p10 have dark tips and the tail is very dark. All in all I would call this one a dark Kumlien’s Gull. But ok, this particular bird is rather easy after all.
The pictures above shows a typical brownie. The tail is rather dark. There seems to be some contrast between inner and outer primaries but it lacks the dark tips. So I would suggest that we’re humble (even though it’s hard) and let these birds go as unidentifiable kumlieni/glaucoides on current knowledge.
To complicate things there are identifiable very pale Kumlien’s Gulls. The bird about was very pale over all, but is has some obviously much darker primaries. The pattern also fits that of Thayer’s Gull quite nicely. So once again: It not about how dark the birds are, but contrast, contrast and contrast. And if the contrast is as obvious as above AND the dark patches seem to fit the pattern of Thayer’s Gull I’d call it a safely identified pale Kumlien’s Gull. Try once more to compare the colour and contrast to the Glaucous Gull – it really is much more obvious and the pattern is different.